This section is ONLY an Adult protocol; however, the practitioner may find this protocol's information useful for pediatric patients and consider use of similar treatment with weight appropriate equivalent doses at their discretion.

Infomation

Anaphylaxis is a multisystem, severe, systemic allergic reaction that results in cutaneous, airway, vascular or GI involvement. Two or more systems should be involved. Typically there has been a previous exposure to the offending agent resulting in anaphylaxis. The key is early recognition and appropriate therapy before this condition progresses to cardiac or respiratory arrest.

Clinical findings by system

• Airway: Upper airway edema, tongue swelling, bronchospasm, laryngeal edema, stridor, rhinitis (early sign)
• Cutaneous: Urticaria, vasodilation, or pallor
• GI: Abdominal pain, vomiting, diarrhea
• Vascular: Hypotension, often profound, due to vasodilation, often with increased capillary permeability

Differential diagnostic considerations

• Severe asthma may actually be anaphylaxis, especially if a second body system is involved.
• ACE-Inhibitor angioedema is not anaphylaxis and typically doesn't respond to anaphylaxis treatment; early airway management is often needed
• Hereditary angioedema may also mimic the airway findings of anaphylaxis, but no urticaria or other signs of anaphylaxis will be present. The treatment is FFP transfusion or C1 esterase inhibitor replacement concentrate.
• Scombroid poisoning occurs within 30 minutes of eating spoiled fish, and has GI toxicity, headache and urticaria, but does well with antihistamines.

Pharmacologic Treatment (see separate section for those in cardiac arrest)

*See important note for patients on ß-Blockers below

1. High Flow O₂
2. Epinephrine
• 0.3-0.5 mg IM (using 1:1,000 conc.) given ASAP and repeated q15-20 min if needed.
• If severe anaphylaxis 0.1 mg of 1:10,000 (1 mL) slowly IV over 5 minutes
• IV Infusion 1-4 mcg/min may be initiated in addition to IM or IV doses above
3. Hypotension should be treated with aggressive fluid resuscitation; typically 1-4 liters rapidly infused depending upon clinical situation.
4. H₁ Antihistamines; typically diphenhydramine (Benadryl®) 25-50 mg IV/IM × 1 dose
5. H₂ Antihistamines
• Cimetidine (Tagamet®) 300 mg PO, IM, IV
• Famotidine (Pepcid®) 20 mg PO, IV
6. Steroids; typically methylprednisolone (Solumedrol®) 125 mg IV slow.

* Note on patients who take ß-Blockers

Patients on ß-Blockers are at increased risk of severe anaphylaxis and can have paradoxical reactions to epinephrine. Patients who are on ß-Blockers with significant anaphylaxis should have glucagon 1-2 mg IV/IM q 5 minutes until stabilized. Additionally, if bronchospasm is present, ipratropium bromide (Atrovent) should be added to nebulized albuterol.

** Note on venom sacs

If a venom sac from a bee sting is present, carefully brush it out using a credit card or sharp edge of a knife tangentially to brush out the stinger from the skin WITHOUT further compressing the venom sac.

*** Note on other therapies

• Vasopressin may have a role in severely hypotensive patients
• Atropine may have a role if bradycardia is present
• Glucagon may have a role in patients unresponsive to epinephrine and in patients on ß-Blockers.

Airway management

Elective intubation should be strongly considered when:

• A patient presents with symptoms of airway obstruction that doesn't rapidly improve with therapy
• A patient develops symptoms of airway obstruction while receiving adequate pharmacologic therapy
• Symptoms of obstruction include hoarse voice, lingual edema, stridor, and angioedema
• These patients are at substantial risk of progressing to where an elective intubation is no longer an option (similar to burn inhalation patients)

Pharmacologic treatment for Cardiac Arrest due to anaphylaxis

• The typical rhythm will be PEA or Asystole; however, prolonged CPR is often indicated, especially in young otherwise healthy patients as success may occur with large amounts of fluids and epinephrine
• Large rapid infusion of fluid through at least 2 large bore IV's (4-8 liters)
• High dose epinephrine is indicated at doses of 1-3 mg IV q3 minutes or 3-5 mg IV q5 minutes
• Epinephrine infusion at 4-10 mcg/min IV
• Antihistamines and steroids can be added but probably have little effect in cardiac arrest
• Glucagon probably indicated; especially if on ß-Blockers
• Vasopressin can be considered in addition to epinephrine

Source: Circulation 2005;112. 2005 AHA Guidelines for CPR and ECC.